Charlie Kimball enjoys a light moment with other drivers during the tests. Some of the top IndyCar teams tested out the track at the Sonoma Raceway Thursday August 7, 2014 in preparation for the Go Pro Grand Prix of Sonoma.

Photo: Brant Ward, San Francisco Chronicle

Charlie Kimball enjoys a light moment with other drivers during the...

When Charlie Kimball drives in an IndyCar race, as he will Sunday at the GoPro Grand Prix of Sonoma, he has a huge fan club rooting for him.

"I'm biased," he said, "but I think the diabetes community is one of the strongest in the world."

Kimball, 29, was diagnosed with Type 1 diabetes seven years ago. He was racing open-wheel cars in Europe and went to a doctor to check on an unrelated skin rash.

"I realized I had lost 25 pounds in just five days," he said, "and my sugars were 5-6 times what they should have been. I guess my blood sugar was so high, I wasn't really thinking clearly."

Six months later, he finished second in his first race. "I remember standing on the podium thinking, not only am I the same competitor, but I'm a better athlete because of this rather than despite it," he said.

When he joined Chip Ganassi Racing in 2011, Ganassi told him not to worry about winning while he learned the ropes from teammates Scott Dixon and Dario Franchitti. Just finish the races, he was told.

Last year he had had enough seasoning. The training wheels were gone. He celebrated his first win at Mid-Ohio, and a lot of fellow diabetics celebrated with him. Winless this year, he stands 13th in the standings.

Novo Nordisk, which makes the insulin he uses and the insulin-delivery systems, has sponsored his car from the start. He monitors his blood sugar during each race. He carries not only a bottle of water like the other drivers, but also a bottle of orange juice and uses a valve to switch between the two.

He said he loves to hear the stories of other diabetics, many of whom have been inspired by his own. "To prove that you can still live your dream has been extremely rewarding," he said. "I hear people say, 'I've always wanted to run a marathon, and I can do it if Charlie can drive a race car.' "

If he ever needed insulin during a race, one of the mechanics would administer it. So far he hasn't needed it.

"In IndyCar, with no power steering and no power brakes, my sugar tends to burn off, so I use less insulin on race day," he said.

Kimball's father, Gordon, is a Stanford-educated engineer; he designed and engineered cars in the old CART series and Formula 1. Kimball was accepted at Stanford but deferred enrollment while he waited to see if his racing career would pan out. It did, so the Farm is still waiting for him.